[chore] Refactor obsreport for scrapers to use new scraper.Metrics

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 90.16393% with 6 lines in your changes missing coverage. Please review.

Please upload report for BASE (main@00fe41b). Learn more about missing BASE report. Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
receiver/scraperhelper/obs_metrics.go	93.18%	2 Missing and 1 partial :warning:
receiver/scraperhelper/scrapercontroller.go	81.25%	2 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #11728 +/- ## ======================================= Coverage ? 91.61% ======================================= Files ? 442 Lines ? 23764 Branches ? 0 ======================================= Hits ? 21772 Misses ? 1620 Partials ? 372 ```

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